High efficiency switching using graphene based electron ``optics''

We demonstrate a way to open a gate-tunable transmission gap across graphene p-n junction by introducing an additional barrier in the middle that replaces Klein tunneling with regular tunneling, allowing us to modulate current by several orders of magnitude. The gap arises by angularly sorting electrons by their longitudinal energy and filtering out the hottest, normally incident electrons with the tunnel barrier, and the rest through total internal reflection. Using analytical and atomistic numerical studies, we show that the barrier causes graphene p-n junction act as a metamaterial with metal-insulator transition and overcome the KTln10/decade limit for subthreshold conduction.